1. Field of the Invention
The present invention relates generally to a semiconductor process, and more specifically, to a semiconductor process, which forms a nitrogen containing liner by performing a decoupled plasma nitridation process and a nitrogen containing annealing process.
2. Description of the Prior Art
In semiconductor processes, in order to provide good electrical isolation and to prevent short-circuits between electric devices on a wafer, a localized oxidation isolation (LOCOS) process, or a shallow trench isolation (STI) process is used to insulate and protect devices. Since the field oxide layer of the LOCOS process consumes a large area on the wafer, and since bird's beaks can occur when growing the field oxide, an STI process is typically used in the semiconductor processes when the line width is below 0.25 μm.
An STI process involves first forming a shallow trench between each device, and then filling the trench with an insulating material to obtain an electrical isolation effect between each device. In modern processes, an oxide will be formed on the side of the trench before the isolating material is filled into the trench, in order to further insulate the isolating material from the surface of the recess. However, as size scales down, the inverse narrow width effect (INWE) becomes more important, leading performances of the semiconductor components to degrade seriously, wherein the inverse narrow width effect (INWE) is the effect of the threshold voltage of a transistor reducing as the channel width of the transistor reduces.
Therefore, a method, which can solve said negative effect is extremely needed to overcome the problems caused by the downscaling of the devices size.